v30

NOAA Technical Report NMFS SSRF- v30

Surface Circulation in the Northwestern Gulf of Mexico as Deduced From Drift Bottles

Robert F. Temple and John A. Martin

May 1979

U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Marine Fisheries Service

NOAA TECHNICAL REPORTS

National Marine Fisheries Service, Special Scientific Report-Fisheries

The major responsihilities of the :>Iational Manne Fishenes ServI('p (;-;:\IFSt arl' to monlt.'r .tod II , •• the abundante find ge.,grllphll distribution of fishery resources, to understand and predi('! Ouctuations in II.,.. quuntlt\ nnd ,it-tnhullon 01 Ihe e "'8<11'" f' • lind 10 ... t,lhil h Ip",l. for optimum use of the resources. NMFS is also charged With the developmenl and 101[>1"01"1111111<'" 01 p"IIcII' for "'lInllg,n~ naIHn,.1 I hlng ~rounds, development and enforcement of domestic fisheries regulalions, surveJilunce ollo"'ll(n IlSlling "II I I1lted "B1I'8 cnl"lal'~ tN ,lind Ih.' development and enforcement of international fisherY a!(reements and polines. :-; MFS nl"IIJS~I. I I h., IIsh,og Industry tnn,ugh mnrhl Ing llervl(" and economic analysis programs, and mortgage lnsuran{'e and ve"el {'onstruet",n .uhs"ite. It ( 111.,(,1.11, anll VII' tnd pu',11 h,'. tatl.tl( Run various phases of the industry

The Special Scientific Report Fisheries senes was established 10 194~J The • en" lIHrtC "'[",rt {In SClI'ntlf.c tnvestlg tlOI1 Ihnt documenl lon~-term continutng programs of ~MFS, or intenSive "Ientlfic reports on sludle, 01 r("tneted", ope '1 h,' rep"rt Ma\ d,'111 With applied fishery problems. The series is also used as a medium for the puhlicatlCln 01 hlhltogruph,cs 01 8 [>I'CI.dl/l·oI III ntille n .• llIrt'

NOAA Technical Reports NMFS SSRF are available free In ilmlterl numh.,,... to J(0vprnr ental n~e'r "S hot h ,',·dNal ond ta e 'I h.,v are o!!iO available in exchange for other scientific and t('rhnical puhlications in th .. mBrine" IPnces InoiJ\t(lunllOJlIt'S rod\ be (J~'tam 'd lunl., oth"rYol ~ notedl from 0825, Technical InformatIOn DIviSion, Environmental SClpnrc Inl/ormatlOn (('nl.'r, ()AA \\.1 hln!:t''" f) ( LO:t ~'j Hennt ,,:-.IH are'

649 Distribution of forage of skipjack tuna (Euth,nnus pelam"'1 10 the eastern tropical Pacific. By Maurice Blackburn and Mlehad Laurs ,Januarv 1972, iii + 16 p., 7 figs .. 3 tables. For sale hy the Superlntendert of Documents, l .S. Government Print,"g Office, Washington, [) (' 20402.

6!;0. Effects of some antioxidants and EDTA on the development of ran cidity in Spanish mackerel (Scomberom )ru.' maculatus) durtng frozen storage. By Robert N. Farragut February 1972, IV + 12 r, 6 fig. Il tables For sale by the Superintendent of Documents, U S Goven men' Prlntmg Office, Washington DC 20402.

6!;1. The effect of premortem stress, holding temperatures, and freeztng on the biochemistry and quality of skipjack tuna. By Lad!'11 Cra .... 1<lrd April 1972, iii + 23 P , 3 figs., 4 tables. For sale by the Superintendent of Documents, C.S. Government Printing Office, Washmgton, l> C 20402.

6!;3. The use of electricity in conjunction with a 1~.'j-meter (Headropel Gulf·of-Mexico shrimp trawl in Lake Michigan By .James E. Ellis March 1972, IV + 10 p., 11 figs., 4 tables. For sale bv the Superintendent of Documents, U.S. Government Printing Office, Washington D.C 20402.

6.54. An electric detector system for recoverin~ internally tagged menhaden, ~enus Brel'oortLG. By R. 0 Parker, .Jr. Februarv 1972. iii + 7 p .. 3 figs., 1 app. table For sale by the Superintendent ~f Documents, U.s. Government Printing Office, Washington, D.C 20402.

6f;!;. Immob1lization of fingerling salmon and trout by decompressIOn By Doyle F. Sutherland. March 1972, III + 7 p., 3 figs., 2 tables. For sale by the Superintendent of Documents, l' S. Government Pnnting Office Washington, D.C 20402. '

6!;6 The calico scallop. Ar{{opecten {{ibbus. By Donald M. Allen and T. ,J. Costello. May 1972, iii + 19 p., 9 figs .. I table. For sale by the Superintendent of Documents, US. Government Printing Office, Washington, D.C 20402.

6!;7. Makin~ fish protein concentrates by enzyrnatic hydrolysis. A status report on research and some processes and products studied bv :-';I\IFS. By Malcolm B. Hale. November 1972, v + 32 p., 15 figs., 17 tables, I app. table. For sale by the Superintendent of Documents US. Government Printing Office, Washington, D.C. 20402. '

65R List of fishes of Alaska and adjacent waters with a guide to some of thetr ilterature. By Ja} C Quast and Elizabeth 1.. Hall. July 1972 IV + 47p. For sale by the Superintendent of Documents, U.S. Gover~ment Pnntmg Office, Washington, 0 C. 20402.

61;9. The Southeast Fisheries Center blOnumeric code. Part I: Fishes. B)~ Harvey R. BU,IIIS: ,Ir., Richard B. Roe, and Judith C. Gatlin. July 19/,2, xl + 9!; p ., 2 fIgs .. For sale by the Superintendent of Documents, LI.S Government Pnntm~ Office, Washington, D.C. 20402.

660. A freshwater fish electro-motivator (FFEMl-its characteristics and operatIon. By ,James E. Ellis and Charles C. Hoopes. November 1972 iii + lip .. 2 fi~s. '

f,V \ ro \" .... (f 'he Ilerature on tl-e deHlopment .,f klPJack tuna ",hl'rl('s '11 Ihe ( ,,1,.1 and ...... tern I'acd (Ocean B\ Fronl< J He ler and riml' Ot lJ .J.]r<lllr) • 71, 11 + : l p 1 fig For ale bv the Sup,'nnt.'ndept 01 J "KUml'I"tH, 1. (;ovl'mmert Prlnttn!! Olflcl> \\d,hl'lgt on, [) C ~040'2

t",~ :-. .. I onll til trt!,u' 0" "I lunas ond billft ht'S Ir the A lantlc H~ ,hn I' \\ e and (harle \\ Ila\l ,Januor) I.ln 1\ .. 24 P , IJ (ig 4

t hl£'s Fllr al!, hv '1]1' uper nlendent of Docllme"'l ,l' (;,,'emment I'rtr'Hlg Off ", II a hn~ton II ( 211102

~"l FI h IJrv Ie C ,1I"cled frorr the ror'hea lern PaCIfiC ( cean and l'uget ,",Olund d mnl( prtl lit: I \18\ 10 B~ Kenneth [) "ald'')n IJ(',p nher f}/2 II. + If> I' Z Itgs I table, lapp tables For all' bv the '> 'j)('rtrtPI, len' If [), {U nent l., (.Q\ernrnent I'rln' nj( (Jrtlce, \\'as'url~" r n (. 2041l;,:

b4'4 Togging d'ld tag H'cnen expertment .... lIh -\Ijantlc menhad£'n, lir" (,urtla t,rl]n11U, Ih Hlchord L Kmlrer and HobNt L [)r\fO<h DeceIT hrr W7:!. \ + I: P j f gs , L tables For sal£' by the. uper'nlen uent If IJr cU'1lenh l .' I.(,H'rn'llent Prm' ng ()fflce, \\o,htngton DC :!0~1J2

116S. Larval ft h -un£'\ 01 Humhrlt Ba\', Caltfornla Bv :\loXlHIl B Elrlnge dnd ('harles F Bnlln Decemher 14~~, II. + 'p, (il:> I to hie For sale I" tt" Supenntendent of DOCUMents, I .' (;overnmeol Pnntlng Ofllre. \\ 'hhlngt on, D (' :eNtl:!.

1~;6. !l ,(ributl< r and relatIve ahundance "I lishes tn :-'ewp{)rt River, "orlh Caroltna Bv \\" lal'" R Turner and Ge<:>rge '\ .Johnson :;eplemb~r 973, 1\ + 2:, r 1 fIt( II table For sale b) the Supertnten­dent 01 DOll'umpnh, l'';; (;"vernment Prtnllng Offlre, \\'ashtngton, D.C. 211402

t)(j~ An -naivs" of the COrrmer1'l8 lohster (Homan .. < am.rlcanu, ftsher, along t he coast "I' \lalOe, Au\:ust 1",1)6 through December 19711. B\ ,lames l' Thomas. ·June 197' "+ ,,7 p If! ltgs ., II tables For saJe b\ the Supertntendent of Documents, l S (;,\\'ernment PnntIOg Oi'l,ce \\'ashin~tnn. D.C 20402

hhll: An annotated hihli' '~raph, of the runner, Tautow,/abrus ad.\per.\u.\ (\\ Ilbaum J B.v Fredrtl' \1 Serrhuk and Da"id W Frame. \Ia\ 1973, ii + ~1 p. For sale hv the Superintendent of Documents. lS Government Prtntlng Office, \Iashln~ton D.C 20402

ll(i9. Subpnint predirtion for dlrert readout meterologlcal satellites Bv 1.. E. Ener. Au~ust 197;], iii + 7 p., 2 fIgs., I tahle. For sale b\ the Supertntendent of Documents. U.S G(\\'ernment Pnnttn/( Office, \\'ashin~ton. DC 20402.

670. l ' nhan'ested fishes in the lIS commercial fishen' of western Lake Erie 10 1969. By Harry 0 \'an I\leter. ,July 1973, III -+- 11 p .. 6 figs., 6 tahles. For sale by the Superintendent of Documents, l' S. Government Printing Office, Washington, D.C 20402.

671 Coastal upwelling indices, west coast of Nort h Ame rica, 1946.71. By Andrew Bakun. June 1973, IV + 103 p., 6 figs., 3 tables, 45 a pl'. figs. For sale by the Superintendent of Documents, U.S Govern ment Print ing Office, Was hington, D.C. 20402.

Continued on Insid b..aclLc.cLve.r....

NOAA Technical Report NMFS SSRF- 730

Surface Circulation in the Northwestern Gulf of Mexico as Deduced From Drift Bottles

Robert F. Temple and John A. Martin

May 1979

U.S . DEPARTMENT OF COMMERCE Juanita M. Kreps , Secretary

National Oceanic and Atmospheric Administration Richard A. Frank, Administrator Terry L. Leitzeli , Assistant Administrator for Fisheries

National Marine Fisheries Service

For Sa le by-the Superintendent of Documents, u.s. Government P rinting Office Washington, D.C. 20402 - Stock No. 003-0 17-00456-2

The National Marine Fisheries Service (NMFS) does not approve, rec­ommend or endorse any proprietary product or proprietary material mentioned in this publication. No reference shall be made to NMFS, or to this publication furnished by NMFS, in any advertising or sales pro­motion which would indicate or imply that NMFS approves, recommends or endorses any proprietary product or proprietary material mentioned herein, or which has as its purpose an intent to cause directly or indirectly the advertised product to be uaed or purchased because of this NMFS publication.

CONTENTS

Introduction ..... . ...................................................... ....... ... ... 1 Methods .................. . ................ ...... . .... ... ........................... 2 Results and discussion ....................... ........ ... .. .... .............. . .. ........ 3

Comparison of ballasted and unballasted drift bottles ......................... ............ 3 Surface circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

January-February . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 March-May. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 June-July ............................................... ....... ....... ....... 8 August. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 September-December . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Literature cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figures

1. The drift bottle study area in the northwestern Gulf of Mexico with the location of stations occupied in 1962 and 1963 .... .. ....... .. ......... ...... . .. . ....... ........................ 2

2. Surface circulation deduced from recoveries of drift bottles released in January 1963 and February 1962 and 1963 in the northwestern Gulf of Mexico ...... ....... .. ........................ 6

3. Surface circulation deduced from recoveries of drift bottles released in March and April 1962 and 1963 in the northwestern Gulf of Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4. Surface circulation deduced from recoveries of drift bottles released in May 1962 and 1963 in the northwestern Gulf of Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5. Surface circulation deduced from recoveries of drift bottles released in June and July 1962 and 1963 in the northwestern Gulf of Mexico. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

6. Surface circulation deduced from recoveries of drift bottles released in August 1963 in the northwest-ern Gulf of Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7. Surface circulation deduced from recoveries of drift bottles relp,ased in September and October 1962 and 1963 in the northwestern Gulf of Mexico .. .. .................. ..................... 11

8. Surface circulation deduced from recoveries of drift bottles released in November 1962 and 1963 and December 1962 in the northwestern Gulf of Mexico .............. . ............... . ....... 12

Tables

1. Numbers of drift bottles released and recovered in the Gulf of Mexico within 0-15 and 16-30 days , by cruises, 1962 and 1963 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. Comparison by cruise of recovery of ballasted and unballasted drift bottles within 30 days after release in the Gulf of Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3. Comparison of the direction and speed of ballasted (B) and unballasted (U) bottles recovered within 15 days after release in the Gulf of Mexico . . .. ...... ... .. . ............................. 5

4. Estimated range and average current velocity for September-December, 1962-63, in the northwestern Gulf of Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

urface Circulation in the Northwestern Gulf of Mexico as Deduced From Drift Bottles l

ROBERT F. TEMPLE and JOHN A. MARTIN2

ABSTRACT

Drift bottles were released monthly at predetermined stations in the northwestern Gulf of Mexico from February 1962 to December 1963. Of the total 7,863 bottles released, 12% (953) were recovered within 30 days after release. Analysis of the monthly recoveries revealed seasonal shifts in the flow of surface waters. Between September and February the dominant flow was west along the Louisiana and east Texas coasts, shiftin g southwest along the southern Texas coast. Between March and May, currents underwent a transitional period, shifting to the north and onshore, particularly along the south and central Texas coast. Converging currents, also apparent along the south Texas coast, ap­peared to progress up the coast with time. In June and July the surface flow was to the northeast and east. August was another transitional period with cur rents appearing to weaken and turning on­shore. Movements of surface waters appeared directly related to prevailing winds .

INTRODUCTION

part of an expanded research effort in 1962 (Kut­nn 1963) , the Bureau of Commercial Fisheries, now • National Marine Fisheries Service, NOAA, initiated rift bottle study to determine the direction and rate of w of surface waters in the northwestern Gulf of Mex­. The objectives of this study were: 1) to document on onthly basis surface current direction and velocity;

tI 2) to attempt to relate monthly variations in current 'ection and speed with the success or failures of the nly shrimp crops. Shrimp are planktonic, and may be endent upon currents for transportation to the estu­

ne nursery grounds, which are essential for successful npletion of their life cycle. The drift bottle study oorted herein began in 1962 and continued through 53. Seasonal difference in direction and speed of surface rrents in the Gulf of Mexico have been generally de­iibed by Smith et a1. (1951), Leipper (1954), Curray ~60), Chew et a1. (1962), and Ichiye (1962). More recent rks on current include those by Drennan (1963), Dren­n et a1. (1963), Armstrong et a1. (1967), Watson and rhrens (1970), Ichiye and Sudo (1971),3 and Moore ~73). Many of the above studies, however, although ntributing to an understanding of ocean currents in the df, were restricted to limited geographic areas and mpleted over relatively short time periods. The data ksented in this report are unique in that they were rerated from the entire northwestern Gulf of Mexico

The compilation, tabulation. and analysis of part of the data reported rein were supported under the Department of Interior's Bureau of Land anagement Interagency Agreement No. 08550-1A5-19. tGulf Fi henes Center. , ational Marine Fisherie ervice. :\'OAA. llveston. TX 77550. 'Ichiye, T .. and H. 'udo. 1971. ep ea waters of the Texas coast. rsity. Ref. 71-19-T. p. 30.

lixing processes between heir and Dep. Oceanogr .. Texas A 1\1 Cni-

and on a monthly basis for a 2-yr period, thus providing a time series heretofore unavailable.

METHODS

Cruises were conducted monthly with chartered shrimp vessels from February 1962 to ovember 1963 to stations located over the continental shelf (Fig. 1). The monthly schedule was followed as closely as possible, the only exceptions being due to adverse weather conditions or mechanical breakdowns. Operations were imilar be­tween years except that fewer stations were occupied in 1963, and one vessel was used to cover the entire tudy area rather than two as in 1962. The general overall ef­fects of these modifications were that in 1963 the areal coverage was slightly reduced, and the time reqUired to provide total coverage of the study area was mcrea ed . The latter effect explains seeming discrepancie m the date labeling of figures used in the analysis to follow For example, the April cruise in 1963 extended into May.

Drift bottles used throughout the tudy were made of clear glass, about 22 cm in height, 6 cm in diameter, and had a capacity of about 240 cm3 . Each bottle contained a bright reddish-orange card on which wa a brief me ' age in Spanish and English. A reward of 50 cent wa paid for the return of the card with information of location and date of recovery. In mo t case, half the bottle relea ed at a station were ballasted (odd numbers) and halt were unballa ted (even numbers). Tho e ballasted floated at or ju t under the urface. The rea on for the u e ul the two types of bottle wa an attempt to determine the direct effect of wind .

The number of bottle relea ed dunng each CCUI

varied during the 2-)'r tudy. Generally, 12 bottle \\ere relea ed at each tation in 1 62; 4-1 0 bottle \\ re relea ed per tat ion in 1 63. Thi modificatiun did not a -feet the rate of recovery for bottle~ withm 30 da~ aft r relea e for the percent recovered m 19 3 \\a ~eat r than

tv

980 W. 960 ,- 92° 90° 300 (H H H H H H 6 H H H A H H A A H A E?h A.A H.E! ? h;9~.~r E; H A 6 A A H E? E! ~ A A H A H 6 A Ej E!:.t\::Jj?;.' A~ 30° N. ! .. ;:] .. If"'IlIlc:.IANA . . '. New Orleans .... ,: .....

28°

26°

TeXAS

0-1962

.-1963

A-1962 & 1963

A GO.I V.??SIOn~ , .'_' __ , ,~ , '.

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Figure I. - The drift bottle study area In the northwestern Gulf of Mexico with the location of ~tlllionA occupied in 1962 and 196~ .

,/

28°

26°

1962 (Table 1) . Thi increa e wa probably due to of the program in 1963 than in

he technique used to depict urface current wa the e as u ed by Day (195 ). Recovered bottle were

uped into two time period of 15 day each, i.e" 0-1 5 sand 16-30 day. The 0-15 day recoverie were fir t tted as traight lines connecting points of relea e and overy. These lines were re olved into directional ar­s, and over these arrow we then plotted, a straight

e , the 16-30 day recoveries. The final tep wa to uce the 16-30 day traight lines to flow arrow con­rning with the 0-15 directional arrow , thu depicting idual drift, not the actual path traversed by a bott le , e reason for the selected groupings and the exclUSIOn bottle recovered after 30 days wa the existence of the d or and-shell beaches throughout the northwestern If of Mexico, and the possibility of bottles drifting ore , remaining intact, but not being found until orne

er date.

Rate of drift, killometers per day , were determined m recoveries made within 15 days after release , In in ­nce where several bottles were returned from a single tion , the bottle or bottles adrift for the shortest time

riod were used to determine rate of drift , Also, if two or

more hottl • r c \ r d r m th rn ad rilt lor the arne P'Tl d of tim but h fe r nt di. tance ,th di tan det rmina tion 01 dn t rat ,

tation in Brown ville and (,alve ton, 1 e ., lind Orlean , La. Ince the time required to rnple CCUI e varied, It wa arbitra rily deC'lded to l n tru t re ul tant wind vector fo r the time penod betv.: !l thl hrst and la t day of each crui~e plus an addltl n I 15 con ecutlve day. The data v.:er comerted to 1 all­fort un it and incorporated into progre. sive v rtor anal ysi , t he length of which mea ured in Beaufort Untl: were di vided by the total number of day. to gl\ a \e ( r average for each penod under con ideration.

Al l dri ft bottle relea e and recovery data u. d In (hl-­report are on file In the, atlOnal Oceanographl Unta Center, Department of Commerc . Wa~hln~t()n. D ( 20235, under Ref. 7 - 35.

Table 1.--Numbers of drUt bottles released and recovered in the Culf of

Mexico 'Within ~15 and 16-30 days, by cruises. 1962 and 1963.

Inclusive Total Rer=2V i:,1t lll % Recovered Cruise Dates Deposited 0-15 16-30 Within 30 daya

1-62 Feb . 17-Feb. 27 651 25 1~ 6

2-62 Mar. 20-Mar. 27 697 27 53 11

3-62 Apr. IS-Apr. 26 690 33 39 10

4-62 May l8-May 22 525 26 11

5-62 June l8-July 1 691 J2 ~5 8

6-62 July l8-Aug. 1 276 21 10 11

7-62 Sep. 7-Sep. 25 663 45 26 11

8-62 Oct. 16-0ct. 30 594 13

9-62 Nov. 14-Dec. 5 697 74 19 11

10-62 Dec. 4-Dec. 19 583 ° 1962 Totals 6,0.7 32b :0 9

1-63 Jan. 22-F~b . 5 l05 1)

2-63 Feb. 19-Mar. q 203 20

.l-63 Har. H-Apr • b ~S, ~1

4-bl Apr. :!l-. v 180 6 9

So-63 "'{ay l1-lU 23 209 57 21

b-b3 June 19-Jun 27 192 .5 )l

7-63 Jul 100July 16 ~O

8-.3 A 17-Au , 31 11

9-63 Sep Z2-<kt .. ]5

10-63 Oct .o-'av 111

I,

RESULTS AND DISCUSSION

Comparison of Ballasted and Unballasted Drift Bottles

Because of the use of two types of bottles, i.e. , ballasted and unballasted, data were grouped by bottle type to determine if differences existed between rates of recovery (Table 2), direction of drift, and speed of drift.

Cruise values of percent recovery fluctuated from 22 to 54% between Cruise 1-62 and Cruise 6-63. Thereafter, values fluctuated from 0 to 76%, reflecting probably the reduced number of bottles released during this period (Table 1). It was readily apparent that in general fewer ballasted than unballasted bottles were recovered with­in 30 days after release (Table 2). For a comparison of direction and speed of ballasted and unballasted bottle drift, we arbitrarily selected 10 "test groups" for anal­ysis, i.e., stations from which several ballasted and un­ballasted bottles were recovered within 15 days from a single release (Table 3).

The average direction of both types of bottles was usually similar. One exception was "test 8" in which several ballasted bottles moved southward down the coast, while several unballasted bottles moved north­ward up the coast. Average speeds were also generally

similar with no definite indication that unballasted bot­tles drifted at a greater rate than did un ballasted bottles.

Surface Circulation

Over the 2-yr period, surface currents underwent distinct directional shifts which were, in general, similar between years. Because of this, specific months, although illustrated individually, have been grouped, irrespective of years: January-February; March-May; June-July; August; and September-December.

January-February.-Currents during this period generally paralleled the northwestern Gulf coast, flowing west off Louisiana and becoming southwest off Texas (Fig. 2). Slight deviations from this pattern were ap­parent in 1962 in two areas. Just west of the Mississippi River the flow was to the north and onshore, whereas off the south Texas coast there were indications of an in­shore countercurrent to the north.

Current velocities ranged from a low of 4 km/day to a high of 14 km/day. Greatest velocities (9-14 km/day) were observed in waters over the central portion of the study area, i.e., off western Louisiana and eastern Texas. Lowest velocities occurred just west of the Mississippi River (5 km/day) and off south Texas (4 km/day) in the vicinity of Brownsville.

Table 2.--Comparison by cruise of recovery of ballas1:ed and unballasted drift bottles within 30 days after release in the Gulf of Mexico

Recoveries Ballasted I Cruise Ballasted Unballasted Total Total Recovered

1-62 29 37 22

2-62 27 53 80 34

3-62 17 55 72 24

4-62 28 37 24

5-62 21 36 57 37

6-62 24 31 23

7-62 19 52 71 27

8-62 14 21 33

9-62 50 43 93 54

10-62 22 31 29

1-63 18 50

2-63 17 17 34 50

3-63 31 51 82 38

4-63 25 45 70 36

5-63 33 45 78 42

6-63 25 31 56 45

7-63 0

8-63 12 15 20

9-63 34 11 45 76

10-63 13 62

11-63 10 70

Totals 366 587 953 38

4

Table 3. -Comparison of the direction and speed of ballasted (B)

and unballasted (U) bottles recovered within 15 days

af ter release in the Gulf of Mexico.

Type Number Direction ~True~ S2eed (km/day) Test Bottle Recovered Range

III B 4

U 230°-276°

112 B 0070-016 °

U 347°-007°

03 B 244°-359°

U

114 B 204°_215°

U 204°-205°

05 B

U 331 °_339°

06 B 292°_307°

U 292°-317°

#7 B

U

118 B 180°-195°

U 195°-009°

09 B

U

1110 B 336°-354°

U 341 °_012°

Resultant wind vectors for the cruise periods revealed differences between areas in the northwestern Gulf as well as differences between months. In January 1963, winds at New Orleans were generally northerly or off­shore, those at Galveston northeasterly or alongshore, and those at Brownsville southeasterly or onshore. This circulation pattern of winds may account for the absence of recoveries of bottles released east of Galveston.

In February 1962 and 1963 winds were generally similar over the entire study area, i.e., east to southeast flowing west alongshore at New Orleans and Galveston and onshore at Brownsville. Strongest winds occurred at Brownsville in both years and probably accounted for the reduced rate of alongshore flow of surface waters observed in that area.

March-May.-Drift bottle movements indicated a transitional period for surface currents in the study area during both years with several distinct features (Figs. 3, 4). First, the flow of surface waters off Louisiana was predominately to the west in March of both years, but as time progressed, the flow direction generally shifted to the north and became onshore in May. This onshore component was more pronounced in May 1962 than in May 1963 when some east to west movement was still ap­parent. Apparent monthly differences in the timing of the breakdown of the dominant east to west movement between years may be accounted for by the difference in cruise dates between years or may reflect real yearly dif-

5

Average Range Average

276° 4.6

268° 1.9.-4.6 4.1

013° 3.7-18.5 9.3

357° 3.7-15.7 11.7

263° 0.9-3.9 1.7

244° 1.1

207° 17.0-21.1 19.8

204° 18.3-19.1 18.7

339° 5.9-6.3 6.1

334° 2.6-6.3 3 .7

302° 2.4-4.8 4.3

305° 2.9-9.3 5.0

298° 6.3

298° 6.3-8.3 7.0

187° 5.6-6.5 6.1

334° 5.6-26.8 10.7

291 ° 25.9-38.9 32.4

291 ° 5.9-38.9 20.0

346° 4.4-7.9 6.7

360° 8.3-14.6 9.8

ferences. Associated with this dominant flow off Loui­siana was a generally weak northward onshore movement of nearshore waters just west of the Mississippi River.

The second prominent feature during this period was the movement of waters off the south Texas coast. Recoveries during both years indicated an area of con­vergence of currents. Furthermore, as the season pro­gressed, this arc of convergence moved northward up the Texas coast until the flow of surface waters became almost directly onshore. In May 1963, however, this pat­tern can only be inferred due to the paucity of drift bottle releases off the south Texas coast.

The third distinct feature of the circulation pattern was the indication of the presence of an oceanic surface current that existed in waters beyond the continental shelf. This was particularly apparent in March of both years and April 1962 when several bottles deposited on the edge of the shelf apparently moved against (straight line trajectory) prevailing shelf currents. From thls set of data, it appeared that in the surface waters three current systems may have been present in the study area: a near­shore countercurrent, a shelf current, and an oceanic cur­rent.

Current velocities varied depending on location with­in the study area. Speeds of the dominant east to west drift off Louisiana ranged between 7 and 14 km/day whereas the weak onshore current just west of the Missis­sippi River ranged from 1 to 3 km/day. Within the area of convergence off Texas, speeds ranged from 3 to 17 km/

T E X A S

JAN. 1963 ,;-,,:;'.--" -"-~-"

, ... {"'_ .. ~~J ....... - .. _-' ,-" ,' ,/

-,---,--' ''; '' 'L .. '/

) ...... /:.; .. : :,>-;~ 28° CDrpu~':""'" :7'~ 1 .. _ .-

ChrISt,· , /'

:' ./ . /

GALVESTON BROWNSVILLE NEW ORLEANS

(

\ / j

o 2 !. ,!

I

L:====~~==~18;3~M~========~======~;;~~;=~=W=='N=D==V~E=C=T=O=R=S==~===B~E~A~U~F~O~R~T~S~;=~ JOOr JO O N

T E X A S

FEB. 1962

98°

T E X A S

FEB. 1963

(

\

+ I

I la3M

96°

.. --" 0(

l ' 'L .. ./

)

/ -. .-"' -

GALVESTON NEW ORLEANS

o 2 I I

WIND VECTORS

/

BROWNSVILLE GALVESTON NEW ORLEANS

~ ~

0 2 26° I ! I I

WIND VECTORS BEAUFORTS

94° 92° 90°

6

Figure 2.-Sur­face circulation deduced from re­coveries of drift bottles released in January 1963 and February 1962 and 1963 in the north­western Gulf of Mexico. (Arrows indica te direction of flow; numbers indicate average km/day).

-J

Q~ O 92 ° 90° 98 0W 96 0 9~ 0 92 ° 90 ° ow 96 ° Js ol I)] )) I n III S IA NA lI' I '"I ---------r--------"TI/TrJ--)T<)r--------,--, n-II-I-S-,A-N-A----r---~<T"--.130 0

T E X A S

MAR . 1962

28 °

26 °

,,-BRO WNSVILLE

~ __ f)

GALVESTON

T E X A S

MAR . 1963

NEW ORLEANS

Gal\leSIOr

~~j~ I BR --./'---

OWNSVILLE

)

'''> _ ~ __ f) A.

GALVESTON NEW ORLEANS I

./ .-

,/

~ -- ~ ~'O :: -J. I I: \ \ I \ US "1;.,-: , ~~. } +

o I 2 1-' ':0:. I 0 I 2

28 °

26°

I MEX ' I... I + WIND VECTORS BE~S MEX I'': I WIND VECTORS I B~TS I, 1,8M 183M -L18M 183 M . I

30 ° , . i I./J J~ I 1 t"\llIr........... i u.. II i I/J J) 1 1r\111C"1... .. .... i .}L.., ,300

N .

T E X A S

APR , 1962

9B O 96 °

BROWNS VILLE GALVESTON

+~ \ WIND VECTORS

94 ° 92°

NEW ORLEANS

\ o I 2 ~

BEAUfORTS

90°

T E X A S Gal,,,,,:.;...;:,,-11~J.l~-r'~>~9---

~~l -r" .:~. "- ) 4'i('~ ~,- ,\ f) A. ./ .-,f 8 1?- - BROWNSVILLE I GALVESTON I NEW ORLEANS

/ 9

1

( ~ \

+ , W'NO "00"' I

1~3M

96 ° 94 ° 92°

1 o I 2 L.........L.o..

BEAU fO RTS

90°

28 °

26 0

Figure 3.-Surface circulation deduced from recoveries of drift bottles released in March and April 1962 and 1963 in the northwestern Gulf of Mexico. (Arrows indicate direction of flow; numbers indicate average km/ day).

T E X A S

MAY 1962

T E X A S

MAY 1963

I

(

'\

/

/

I

(

'\

f 183M

98° 96°

BROWNSVILLE

94°

\ WIND VECTORS

'- ") - "\..\"~ .. _.ft."­

GALVESTON

\ WIND VECTORS

92°

o I

2 ! I

NEW ORLEANS

0 2 I I I

BEAUfORTS

90°

26°

I' ur 4. ~urfa~ circulation deduced trom recoveries ot drift bottles releaeed In May 1962 and 1963 In the northwestern Gulf of Mexico. (Arrows indicate direction of flow; numbers indicate average km/day).

with an over 11 a\ erage of about 6. In general veloc­I f urface current decrea ed from :\larch to Mayas r nt b arne more on:shore.

e ptl n , .... md were generally similar be­\er the tud) rea, but a marked seasonal

pparent. Re ultant wind vectors nd became more outherly or on-

m penod nd may account for the f th e t to we t flow of surface

waters off Louisiana and east Texas as well as a shift in surface currents to the north off south Texas. With the exceptlOn of May 1962, wind force was greatest at Brownsville.

June-July.-Following the March-April transitional period, the dominant east to west flow of January­February had in essence reversed (Fig. 5). Currents flowed northward along the south Texas coast, whereas

to

98° W. 300~

N.

T E X A S

JUN . 1962

28 °

9 6° 94° 92° 90°

<:Y G';;P ,","" '-'-. A 4f~:' 't\"?---,·:: ',' ---- .- ... _} . ): TO --.../

, 5 FL OR"""'" ' ( __ ~ ) ID ...

/4 (/ _ f)r-. ~

/

/

/"

I~ ~ ./'-""'-'> \J--~ BROWNSVILLE I GALVESTON I NEW ORLEANS

96° 94° 92° 90° 1)1·', ,(\. .0 130 0

T E X A S

JU N. 1963

/ /

-- --- -- ../'" --' ,-,>-'\J-

f)r-. ./ - ~28 °

BROWNSVillE GALVESTON NEW ORLEANS

__ III \\ : ~

,J?1" ,~'" ,n" w," .~"O" 1 .. ~" 11 ' 1+ '" \ , · . _...... 183M I 2 .. .IL WIND VECTORS ~ III ' 1\ BEAUFORTS

. ........... . •. . iJ_ . 30 0

26° ~\ + WIND VECTORS

T E X A S

JUL. 1962

-----./"'.-/

BROWNSVILLE

+~ 98° 96° 9 4°

'- '> - ' \J _ . - f) r-.

GALVESTON

I WIND VECTORS

92°

)

./ -NEW ORLEANS

~

o I 2 .L.......L...._ '

BEAU FORTS

90°

T E X A S

JUL. 1963

I

/

/

\

I 1~3 M

/"

96°

,. , ..... - . u.....- _'1

BROWNSVILLE GALVESTON

\ WIND VECTORS

+\ 94° 92°

". '-- /

)

./ -NEW ORLEANS

! o I 2 ~

BEAUFORTS

90°

/

28 °

26°

Figure 5.-Surface circulation deduced from recoveries of drift bottles released in June and July 1962 and 1963 in the northwestern Gulf of Mexico. (Arrows indicate direction of flow; n umbers indicate average km/ day).

off Louisiana currents were to the north or east with the northerly current generally restricted to nearshore waters and the eastward movement restricted to the deeper waters over the shelf. The strength of this eastward flow was apparently greater in 1962 than in 1963 as evidenced by the recovery of bottles as far away as Florida within 30 days after release. In 1963, bottles were also recovered in Florida but time adrift exceeded 30 days and the recoveries therefore are not shown in Figure 5.

Current velocities varied throughout the study area with values ranging from 3 to 12 km/day along the Texas coast and averaging 7 km/day. Onshore currents along the Louisiana coast ranged from 1 to 9 km/day with an average of 3 km/day. Monthly velocities were similar be­tween years.

The influence of the prevailing southerly wind so char­acteristic of the summer in the northwestern Gulf of Mexico was readily apparent at Brownsville and Galveston for June and July of both years. Surface water currents off Texas were observed flowing either directly downwind or slightly to the right of the prevailing wind directlOn. Off Louisiana, however, the wind direction varied between years. In 1962, air flow was to the east whereas in 1963 it was more to the north. This variation generally supports the stronger eastward movement of surface waters off Louisiana in 1962.

August.-Drift bottles were released during this time period only in 1963, and their movements indicated still another transitional period in current direction and

T E X A S

AUG. 1963

/

I

I

\

I 183M

BROWNSV ILLE

94°

velocity (Fig. 6). Surface currents, rather than moving alongshore and to the north, had shifted to onshore toward t he west; velocities had slowed to a rate of 2-3 km/day, a marked decrease from those velocities observed in the June-July period.

At Brownsville and Galveston winds were generally southeasterly. At New Orleans, winds were variable, as evidenced by the relatively small resultant vector, and were northwesterly.

September-December.- The release and recovery of drift bottles indicated that surface currents had returned to the dominant flow noted in January-February, i.e., a general west to southwesterly flow (Figs. 7, 8) . Several features of the circulation pattern, however, should be noted. First, recoveries of bottles in the vicinity of Brownsville, Texas, in 1962 indicated a westerly onshore movement that dissipated as the season progressed.

Second, the onshore component of the prevailing southwest current was not as apparent in 1963 as in 1962. Few bottles released in the study area were recovered within 30 days, and of those that were , most were released at nearshore stations. Whether this was due to the lack of areal coverage or the total number of bottles released is not known, but the results were similar to those observed in December 1962 (Fig. 8) , a period when a large number of bottles were released and areal coverage was extensive. This absence of recoveries may indicate either an along- or offshore movement of surface waters.

--, .: ~ )

.. --"

.-----

'> ... 'L .. . ./

)

,-S-"'\.l·.~ _ . ..'1 .. /'-. .. / ... ..-

GALV ESTON NEW ORLEANS

\ 0 2

! I

WIN D V ECTORS BEAUFORTS

92 ° 90°

/

26°

f ilture h.-Surface circulation deduced from recoveries of drift bottles released in August 1963 in the northwestern Gulf of Mexico. (Arrows indicate direction of flow; numbers indicate average km/day).

10

... ...

98°W . 300~

N.

96° 90° 92 ° 90° 96 ° 300

I/r )) 1I""IIIII;.IAttJA ij; I

28 °

30°' N.

98 °

Ex A S G7"""o.n).;; ~ ____ , '_, r '7 ~. _ ._ .. _. _', SEP . 1962 .. /~:--?_ ':, ____ _ ___ ,

': ~ .'/",'

.• ~~~ 11r--

r '~~. ~ _ ,~ __ ,\~_~_ .. ::

~ '- /'

)

./ ~

NEW ORLEANS

T E X A S

SEP. 1963 G'IV"to~ ~.- .. _-. _____ ,_

,~:~,./ .. : .

/ ~

.. ~9-'-" _.'.\ __ 11

r--./~

, ....

~ '- /'

)

/

28°

.'//~-~r'" I

.' 51"': / I 0"

Chllll'l' I , ~

, 4 ,.."om ~frt~ "'----------- ~ I ~ , WINO "",0_','" .. ", .v. "0' ' II \ ° , , "" In J\ ,, ~ + ~ . ' ,om '?3-

4

: WIN ° "00"."", '''" I .~ ." IBM 183 M III". 'J \- .

. ;;~ 11 ,: -

BROWNSVILLE GALVESTON NEW ORLEANS

I 26°

/ /"

T E X A S

OCT. 1962 ,-.:, .. -- ..

--- ----./'"'.-"" ,-,,_.'.\ __ 11 r--

./ BROWNSVILLE GALVESTON

~ ~

+ WIND VECTORS

96 ° 94 ° 92°

: .. ' ,.:,'

~ '- /'

)

./ -NE W OR LEAN S

J o I 2 ~

BEAUFO RTS

90°

/ ~."ves~o;7 ~ __ _

,;y .. ?r:='·-' -------- ___ _ / '" ......-

.,\ .....- .. - 11r--

./ BROWNSVILLE GALVESTON

I

I

I

'\

I \~

\ ~

+ WIND VECTORS

96 ° 94 ° 92 °

~ . ./ . -

~ ' 'L. " /'

)

NEW ORLEANS

/ 0 I 2 ~

BEAUFORTS

90°

/

28°

H26°

Figure 7. - Surface circulation deduced from recoveries of drift bottles released in September and October 1962 and 1963 in the northwestern Gulf of Mexico. (Arrows indicate direction of flow; numbers indicate a average km/day).

98°W. 30° N.

T E X A S

NOV. 1962

28°

T E X A S

NOV. 1963

T E X A S

DEC. 1962

28°

MEX

98°

I

I

\

I

I

\ }

I

/

/

183M

96°

BROWNSVillE

BROWNS IllE

/" BROWNSVilLE

96° 94°

91°

\l ------r---GALVESTON w

/

CAlVESTO

.:

1 __ '1"- ./ -GALVESTON NEW OlllEA S

/ I o 2

WIND VECTORS I ! I

8EAUFORTS

92° 90°

12

/ I~ .-. uria

clrculallon dt­duetd from rt· co, ~ of drift bolll reltaHd in

18° NOHmbtr 19&2 and 1 63, and ~mboor 1961 in lht north... ttom

Gulf of Mnico . Arrow indicalt d.irecdon of now; numboon indica", av~ e lun/day).

26°

able 4.-EBtimated range and average current veloci ty for September­

Deoember 1962-63 in the northweetern Gulf of Mexico.

1962 1963 Ran e Avera e Range Average

eptember 1-10 8-9

October 2-4 no data

November 2-12 no data

December 2-5 no data

Information on current velocities was generally restricted to the 1962 data, but no distinct trend was readily apparent. Ranges and averages for each month are shown in Table 4.

The seasonal shift in wind circulation over the study area during this period agreed generally with the direc­tion of surface water movement. With few exceptions, east to southeast winds became more northerly until in November 1963 and December 1962 north winds dominated over the entire study area. The lack of drift bottle recoveries during this period supports the implied offshore southerly flow of surface waters.

LITERATURE CITED

ARMSTRONG, R. S., J . R. GRADY, and R. E. STEVENSON. 1967. Cruise "Delta I" of the "Geronimo". Commer. Fish. Rev.

29(2) :15-18. CHEW, F., K. L. DRENNAN, and W. J . DEMORAN.

1962. Some results of drift bottle studies off the Mississippi Delta. Limnol. Oceanogr. 7:252-257.

13

C 1960. Sediments and history of Holocene tranagr lon, conlin n­

tal shelf, northwest Gulf of Mexico. In hepe.rd , F. P., F. B. Phieger, and T. H. van Andel (edItors), Gulf of ~1exlco, p 221· 266. The Colleg:tate Press, Menll8ha, Wis.

DAY, C. G. 1958. Surface circulation in the Gulf of Mame Il8 deduced (rom

drift bottles. US. Fish Wildl . Serv., Fish. Bull. 58 :'43-472 DRENNAN, K.

1963. Surface circulation in the northell8tern Gulf of Mexico. Gulf Coast Rea. Lab., Oceanogr. Sec., Tech. Rep., 116 p.

DRENNAN, K. L., W. J. DEMORAN, and R. D. GAUL. 1963. Some results of recent circulation studies east of the ~f

sippi delta . (Abstr.) Trans. Am. Geophys . Uruon 44 61. ICHIYE, T.

1962. Circulation and water mass distribution in the Gulf of Mex ico. Geofis. Int. (Mexico City) 2(3):46-76.

KUTKUHN, J . H. 1963. Expanded research on Gulf of MeXICO shnmp resource. Proc

Gulf Caribb. Fish. Inst., 15th Ann. Sess., 1962:65-78. LEIPPER, D. F.

1954. Physical Oceanography of the Gulf of Mexico. In P. A. Galt· soff (coordinator), Gulf of Mexico, its origin, waters, and manne life, p. 119-137. U.S. Fish Wildl . Serv., Fish. Bull 55

MOORE, G. T. 1973. Submarine current measurements - northwest Gulf of Mex .

ico. Trans. Gulf Coast Assoc. Geol. Soc. 23;245-255 , SMITH, F. G. W., A. F. MEDINA, and A F. B. ABELLA.

1951. Distribution of vertical water movement calculated from lur· face drift vectors. Bull. Mar. Sci. Gulf Caribb. 1:187-195.

U.S. DEPARTMENT OF COMMERCE. 1962-1963a. Local climatological data, Brownsville, Teu8 .

Weather Bureau. 1962-1963b. Local climatological data, Galveston, Texas . Weather

Bureau. 1962-1963c. Local climatological data, New Orle8.ll8, Louisiana .

Weather Bureau . WATSON, R. L., and E. W. BEHRENS.

1970. Nearshore surface currents, southeastern Texll8 Gulf Coast. Contr. Mar. SCI. 15:133-143.